v126: Mailman UnicodeDecodeError error when sending digests

Symptoms

Opening the mailing list returns "Internal Server Error" while processing digests. Digests return the following error when sending:

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf3 in position 45: invalid continuation byte

Mar 26 19:10:50 2025 (3741876) send_digests() failed: a bytes-like object is required, not 'str'

Note: This error is returned in the mailman error log "/usr/local/cpanel/3rdparty/mailman/logs/error".

Description

Since upgrading to cPanel version 126, Mailman uses Python 3. Some UTF-8 encodings in the digest emails return errors, which prevent the list from opening. If digests are enabled, the list will be locked when sending digests.

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-46529. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

None available.